Many locks of the pin tumbler type include an indentifying key code. This key code indicates the order and various height of the serrations of the key which are necessary to operate the particular lock. Ordinarily, when a duplicate key is required for a lock of this type, a duplicate key is simply cut from an appropriate blank using the original key as a master. Machines for cutting a duplicate key from a master key of this type are well known to those of ordinary skill in the art. However, where a key to the lock is no longer available (typically lost), it is a relatively laborious and time consuming process to construct a new key from a suitable blank even where the height of the serrations is known from the key code of a lock.
In order to cut a new key for a lock where no key currently is available, it has been proposed in the prior art to use a simple key duplicating machine as disclosed in U.S. Pat. No. 3,791,240 (Meoni). According to the disclosure in this patent, this is accomplished by providing a plurality of master blanks each one of which is individually sized to produce a cut at a single certain location and to a single certain depth. While such a method would be successful, it is apparent that a great number of master blanks are necessary. In addition, it is relatively time consuming to clamp, cut and then unclamp each master blank for each serration which must be cut in the duplicate key.
Also disclosed in the prior art is a method for cutting blank keys using the lock cylinder from the lock. These methods are disclosed in U.S. Pat. No. RE 26,848 (Simon) and U.S. Pat. No. 1,254,442 (Smith). According to this method, the lock cylinder is removed from the lock and a blank (uncut) key is inserted in the lock cylinder. This causes the cylinder pins to extend from the lock cylinder a distance corresponding to the depth of cut needed in a blank key to fit this lock cylinder. A special apparatus is then needed for cutting a blank key at locations and to a depth corresponding to the pins sticking up from the lock cylinder.